Abstract
Allelopathic substances can be used to develop weed control alternatives based on natural products. The objective of this study was to compare the phytotoxic activity of aqueous leaf extracts of Rapanea umbellata with the toxicity of a synthetic herbicide on the germination and growth of weed species. The weeds species barnyard grass (Echinochloa crus-galli), wild poinsettia (Euphorbia heterophylla) and morning glory (Ipomoea grandifolia) were used. The effects of the aqueous leaf extract of R. umbellata at concentrations of 10% and 5% (g mL -1 ) were compared to the control (distilled water) and to the synthetic herbicide oxyfluorfen. The average weed germination time was significantly lower (p < 0.05) in control than in extract and herbicide treatments. The herbicide had more significant effects than the extract on the initial growth of the aerial part. However, the initial growth of the root part was significantly more affected by the leaf extract than by the herbicide. The extract also caused many disorders in weed root anatomy. Therefore, the leaf aqueous extract of R. umbellata showed important results that indicate that it should be bioprospected and that its allelochemicals should be purified for the discovery of natural-origin herbicides.
Highlights
Weed management has been a problem since the beginning of agriculture
The aim of this study was to compare the effects of R. umbellata leaf aqueous extract with the effects of a synthetic herbicide on the germination and growth of weeds: wild poinsettia, barnyard grass, and morning glory
There was no effect of PEG at -0.1 and 0.2 on the germination percentage and average time, and weeds initial growth
Summary
Weeds show higher specific leaf area and are more competitive than other plant species because they are better colonizers, reproduce themselves faster and survive in more adverse situations (COLAUTTI et al, 2006; HAMILTON et al, 2005). They are frequently annual or biannual, smaller and more toxic to herbivorous species Different types of synthetic herbicides are used to control weeds. Synthetic herbicides are highly effective in low concentrations, show good selective action and are relatively cheap
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